一、概述

​ 因为gstreamer没有提供qnx系统的支持， 因此这里要实现音频和视频的播放，就必须自己实现最终的音视频输出的元件，即sink元件，一开始，我的想法是，可否移植开源的音视频输出库，比如sdl，alsa等等， 但是发现有些麻烦， 反而把事情弄的更复杂了。 最终还是踏踏实实的两个gstreamer的sink元件，用来输出音频和视频。

​ 要编写gstreamer的插件有很多方式， 比如直接“继承”实现GstElementClass和GstElement，使用gst-template工具创建一个插件模板，然后去实现。 我这里使用的另一种方式， 既然是实现sink类型的元件。 那么就直接找gstreamer已有的sink元件作为模板，将他们复制过来，删除原有的接口实现代码，换上自己的实现。

注意， 输出的plugin动态库名称以 libpluginname.so 的形式， 而这个pluginname就是 编写插件时，定义插件的宏GST_PLUGIN_DEFINE 的参数中的name， 如果不匹配，就会出现插件无法是使用，被gstreamer将插件加入黑名单

二、实现QNX audio sink插件

其实gstreamer有sink插件的“基类”：GstAudioSinkClass， 我们要做的就是继承和override一些接口。GstAudioSinkClass的全部接口如下：

struct _GstAudioSinkClass {/**基类，其完成的继承路径是 GSTAudioSinkClass ——> GstAudioBaseSinkClass ——>GstBaseSinkClass ——> GstElementClass ,再向上就是和gobject相关的东西了，这里不涉及 */  GstAudioBaseSinkClass parent_class; /* vtable， 接口定义 *//* open the device with given specs， 打开设备*/gboolean (*open)      (GstAudioSink *sink);/* prepare resources and state to operate with the given specs， 进行prepare操作 */gboolean (*prepare)   (GstAudioSink *sink, GstAudioRingBufferSpec *spec);/* undo anything that was done in prepare()， 回退到prepare之前 */gboolean (*unprepare) (GstAudioSink *sink);/* close the device， 关闭设备 */gboolean (*close)     (GstAudioSink *sink);/* write samples to the device， 向音频设备写数据 */gint     (*write)     (GstAudioSink *sink, gpointer data, guint length);/* get number of frames queued in the device，获取设备队列里面有多少帧没有输出(即缓存) */guint    (*delay)     (GstAudioSink *sink);/* reset the audio device, unblock from a write，重置设备 */void     (*reset)     (GstAudioSink *sink);/*< private >*/gpointer _gst_reserved[GST_PADDING];
};

​ 我这里就是以oss音频 sink插件作为模板，将其源码复制出来，删除基于oss接口实现的 gstreamer audio sink接口的代码，然后再填充自己的代码， 其中 头文件 gstQnxAudioSink.h, 其内容如下：

/* GStreamer* Copyright (C) gu.wen <454727014@qq.com>** gstqnxaudiosink.h: **/#ifndef __GST_QNXAUDIO_H__
#define __GST_QNXAUDIO_H__#include <gst/gst.h>
#include <gst/audio/gstaudiosink.h>
#include <glib/gtypes.h>
#include <sys/asoundlib.h> /** 包含qnx audio接口的头文件 */G_BEGIN_DECLS
/** 定义方面操作的工具宏 */
#define GST_TYPE_QNXAUDIOSINK (gst_qnxaudio_sink_get_type())#define GST_QNXAUDIOSINK(obj) (G_TYPE_CHECK_INSTANCE_CAST((obj), \GST_TYPE_QNXAUDIOSINK, \GstQnxAudioSink))#define GST_QNXAUDIOSINK_CLASS(klass) (G_TYPE_CHECK_CLASS_CAST((klass), \GST_TYPE_QNXAUDIOSINK, \GstQnxAudioSinkClass))#define GST_IS_QNXAUDIOSINK(obj) (G_TYPE_CHECK_INSTANCE_TYPE((obj), \GST_TYPE_QNXAUDIOSINK))#define GST_IS_QNXAUDIOSINK_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE((klass), \GST_TYPE_QNXAUDIOSINK))typedef struct _GstQnxAudioSink GstQnxAudioSink;
typedef struct _GstQnxAudioSinkClass GstQnxAudioSinkClass;struct _GstQnxAudioSink
{GstAudioSink sink; /** 继承audio sink， 这个成员变量必须放在首位 */gchar *device;  /** qnx audio 设备节点的路径 */gint audioCard; /** 声卡id */gint bytes_per_sample; GstCaps *probed_caps;  /** 存放检索到的caps信息 *//** qnx audio 相关的 数据结构 */snd_pcm_info_t info; snd_pcm_t *pcm_handle;snd_pcm_channel_info_t channelInfo;snd_mixer_t *mixer_handle;snd_mixer_group_t mixerGroup;snd_pcm_channel_params_t channelParam;snd_pcm_channel_setup_t channelSetup;
};struct _GstQnxAudioSinkClass
{/**类，用于定义接口，其完成的继承路径是 * _GstQnxAudioSinkClass ——> GSTAudioSinkClass ——> GstAudioBaseSinkClass * ——> GstBaseSinkClass ——> GstElementClass* 再向上就是和gobject相关的东西了，这里不涉及 */GstAudioSinkClass parent_class;
};/** 获取GType，具体的参考 gobject/glib相关的信息 */
GType gst_qnxaudio_sink_get_type(void);G_END_DECLS#endif /* __GST_QNXAUDIO_H__ */

接下来再试重点, qnx audio sink 的实现源文件， 如下所示：

/* GStreamer* Copyright (C) gu.wen <454727014@qq.com>** gstqnxaudiosink.c: **//*** SECTION:element-qnxaudio** This element lets you output sound using the qnx audio system (QNXAUDIO).** Note that you should almost always use generic audio conversion elements* like audioconvert and audioresample in front of an audiosink to make sure* your pipeline works under all circumstances (those conversion elements will* act in passthrough-mode if no conversion is necessary).** <refsect2>* <title>Example pipelines</title>* |[* gst-launch-1.0 -v audiotestsrc ! audioconvert ! volume volume=0.1 ! qnxaudio* ]| will output a sine wave (continuous beep sound) to your sound card (with* a very low volume as precaution).* |[* gst-launch-1.0 -v filesrc location=music.ogg ! decodebin ! audioconvert ! * audioresample ! qnxaudio ]| * will play an Ogg/Vorbis audio file and output it using the Open Sound System.* </refsect2>*/#ifdef HAVE_CONFIG_H
#include "config.h"
#endif#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>#include "gstQnxAudioSink.h"#define PLUGIN_VERSION "00.01.00"
#define PACKAGE "gst-plugins-qnx"
#define GST_LICENSE "LGPL"
#define GST_PACKAGE_NAME "GStreamer qnx Plug-ins source release"
#define GST_PACKAGE_ORIGIN "Unknown package origin"GST_DEBUG_CATEGORY_EXTERN(qnxaudio_debug);
#define GST_CAT_DEFAULT qnxaudio_debugstatic void gst_qnxaudio_sink_dispose(GObject *object);
static void gst_qnxaudio_sink_finalise(GObject *object);static void gst_qnxaudio_sink_get_property(GObject *object, guint prop_id,GValue *value, GParamSpec *pspec);static void gst_qnxaudio_sink_set_property(GObject *object, guint prop_id,const GValue *value, GParamSpec *pspec);static GstCaps *gst_qnxaudio_sink_getcaps(GstBaseSink *bsink, GstCaps *filter);static gboolean gst_qnxaudio_sink_open(GstAudioSink *asink);
static gboolean gst_qnxaudio_sink_close(GstAudioSink *asink);
static gboolean gst_qnxaudio_sink_prepare(GstAudioSink *asink,GstAudioRingBufferSpec *spec);
static gboolean gst_qnxaudio_sink_unprepare(GstAudioSink *asink);
static gint gst_qnxaudio_sink_write(GstAudioSink *asink, gpointer data,guint length);
static guint gst_qnxaudio_sink_delay(GstAudioSink *asink);
static void gst_qnxaudio_sink_reset(GstAudioSink *asink);/* QnxAudioSink signals and args */
enum
{LAST_SIGNAL
};#define DEFAULT_DEVICE "/dev/snd/pcmPreferredp"enum
{PROP_0,PROP_DEVICE,
};#define FORMATS "{" GST_AUDIO_NE(S16) "," GST_AUDIO_NE(U16) ", S8, U8 }"/** 定义 固定pad的工厂 */
static GstStaticPadTemplate qnxaudio_sink_factory =GST_STATIC_PAD_TEMPLATE("sink",GST_PAD_SINK,GST_PAD_ALWAYS,GST_STATIC_CAPS("audio/x-raw, ""format = (string) " FORMATS ", ""layout = (string) interleaved, ""rate = (int) [ 1, MAX ], ""channels = (int) 1; ""audio/x-raw, ""format = (string) " FORMATS ", ""layout = (string) interleaved, ""rate = (int) [ 1, MAX ], ""channels = (int) 2, ""channel-mask = (bitmask) 0x3"));/* static guint gst_qnxaudio_sink_signals[LAST_SIGNAL] = { 0 }; */#define gst_qnxaudio_sink_parent_class parent_classG_DEFINE_TYPE(GstQnxAudioSink, gst_qnxaudio_sink, GST_TYPE_AUDIO_SINK);static void gst_qnxaudio_sink_dispose(GObject *object)
{   /** override GObjectClass 的dispose接口 */GstQnxAudioSink *qnxaudio = GST_QNXAUDIOSINK(object);if (qnxaudio->probed_caps){/**如果已经索引过qnx audio sink 的能力， 就是放已有的caps信息 */gst_caps_unref(qnxaudio->probed_caps);qnxaudio->probed_caps = NULL;}/** 再调用父类的dispose接口 */G_OBJECT_CLASS(parent_class)->dispose(object);
}static GstStructure *
gst_qnxaudio_helper_get_format_structure(unsigned int format_bit)
{/** 根据qnx audio的类型生成caps信息的结构体 */GstStructure *structure;//printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);const gchar *format;switch (format_bit){case SND_PCM_SFMT_U8:format = "U8";break;case SND_PCM_SFMT_S16_LE:format = "S16LE";break;case SND_PCM_SFMT_S16_BE:format = "S16BE";break;case SND_PCM_SFMT_S8:format = "S8";break;case SND_PCM_SFMT_U16_LE:format = "U16LE";break;case SND_PCM_SFMT_U16_BE:format = "U16BE";break;default:g_assert_not_reached();//printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return NULL;}printf("[%s.%d]===>:format: %s\n", __FUNCTION__, __LINE__, format);structure = gst_structure_new("audio/x-raw","format", G_TYPE_STRING, format,"layout", G_TYPE_STRING, "interleaved", NULL);return structure;
}static GstCaps *
gst_qnxaudio_helper_probe_caps(snd_pcm_channel_info_t *channelInfo)
{/** 索引qnx audio的能力信息 *///printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);
#if G_BYTE_ORDER == G_LITTLE_ENDIANconst guint probe_formats[] = {SND_PCM_SFMT_S16_LE, SND_PCM_SFMT_U16_LE, SND_PCM_SFMT_U8, SND_PCM_SFMT_S8};
#elseconst guint probe_formats[] = {SND_PCM_SFMT_S16_BE, SND_PCM_SFMT_U16_BE, SND_PCM_SFMT_U8, SND_PCM_SFMT_S8};
#endifGstStructure *structure;GstCaps *caps;int f;/* FIXME test make sure we're not currently playing *//* FIXME test both mono and stereo */caps = gst_caps_new_empty();/* assume that the most significant bit of format_mask is 0 */for (f = 0; f < G_N_ELEMENTS(probe_formats); ++f){printf("[%s.%d]===>:idx:%d, rate range(%d - %d)\n", __FUNCTION__, __LINE__, f, channelInfo->min_rate, channelInfo->max_rate);GValue rate_value = {0};/* one big range */g_value_init(&rate_value, GST_TYPE_INT_RANGE);gst_value_set_int_range(&rate_value, channelInfo->min_rate,(channelInfo->max_rate == -1) ? channelInfo->min_rate : channelInfo->max_rate);structure = gst_qnxaudio_helper_get_format_structure(probe_formats[f]);gst_structure_set(structure, "channels", GST_TYPE_INT_RANGE, 1, 2, NULL);gst_structure_set_value(structure, "rate", &rate_value);g_value_unset(&rate_value);gst_caps_append_structure(caps, structure);}if (gst_caps_is_empty(caps)){/* fixme: make user-visible */GST_WARNING("Your qnx audio device could not be probed correctly");}else{caps = gst_caps_simplify(caps);}printf("[%s.%d]===>:probed caps: %p\n", __FUNCTION__, __LINE__, caps);GST_DEBUG("probed caps: %" GST_PTR_FORMAT, caps);return caps;
}static void gst_qnxaudio_sink_class_init(GstQnxAudioSinkClass *klass)
{/** 类初始化接口 *///printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);GObjectClass *gobject_class;GstElementClass *gstelement_class;GstBaseSinkClass *gstbasesink_class;GstAudioSinkClass *gstaudiosink_class;gobject_class = (GObjectClass *)klass;gstelement_class = (GstElementClass *)klass;gstbasesink_class = (GstBaseSinkClass *)klass;gstaudiosink_class = (GstAudioSinkClass *)klass;parent_class = g_type_class_peek_parent(klass);/** override 父类接口 */gobject_class->dispose = gst_qnxaudio_sink_dispose;gobject_class->finalize = gst_qnxaudio_sink_finalise;gobject_class->get_property = gst_qnxaudio_sink_get_property;gobject_class->set_property = gst_qnxaudio_sink_set_property;/** 安装属性接口 */g_object_class_install_property(gobject_class, PROP_DEVICE,g_param_spec_string("device", "Device","QNXAUDIO device (usually /dev/dspN)", DEFAULT_DEVICE,G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));/** override 父类接口 */gstbasesink_class->get_caps = GST_DEBUG_FUNCPTR(gst_qnxaudio_sink_getcaps);gstaudiosink_class->open = GST_DEBUG_FUNCPTR(gst_qnxaudio_sink_open);gstaudiosink_class->close = GST_DEBUG_FUNCPTR(gst_qnxaudio_sink_close);gstaudiosink_class->prepare = GST_DEBUG_FUNCPTR(gst_qnxaudio_sink_prepare);gstaudiosink_class->unprepare = GST_DEBUG_FUNCPTR(gst_qnxaudio_sink_unprepare);gstaudiosink_class->write = GST_DEBUG_FUNCPTR(gst_qnxaudio_sink_write);gstaudiosink_class->delay = GST_DEBUG_FUNCPTR(gst_qnxaudio_sink_delay);gstaudiosink_class->reset = GST_DEBUG_FUNCPTR(gst_qnxaudio_sink_reset);/** 设置qnx  audio sink 元件的meta信息 */gst_element_class_set_static_metadata(gstelement_class, "Audio Sink (QNXAUDIO)","Sink/Audio","Output to a sound card via QNXAUDIO","guwen <454727014@qq.com>");/** 添加固定pad工厂 */gst_element_class_add_static_pad_template(gstelement_class,&qnxaudio_sink_factory);//printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);                                              
}static void gst_qnxaudio_sink_init(GstQnxAudioSink *qnxaudio)
{/** qnx audio sink数据结构初始化 */GST_DEBUG_OBJECT(qnxaudio, "initializing qnxaudio");//printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);qnxaudio->pcm_handle = NULL;qnxaudio->mixer_handle = NULL;qnxaudio->audioCard = -1;qnxaudio->probed_caps = NULL;qnxaudio->device = strdup(DEFAULT_DEVICE);memset(&qnxaudio->channelInfo, 0, sizeof(qnxaudio->channelInfo));memset(&qnxaudio->channelParam, 0, sizeof(qnxaudio->channelParam));memset(&qnxaudio->channelSetup, 0, sizeof(qnxaudio->channelSetup));memset(&qnxaudio->mixerGroup, 0, sizeof(qnxaudio->mixerGroup));//printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);
}static void gst_qnxaudio_sink_finalise(GObject *object)
{/** override finalise接口 *///printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);GstQnxAudioSink *qnxaudio = GST_QNXAUDIOSINK(object);g_free(qnxaudio->device);G_OBJECT_CLASS(parent_class)->finalize((GObject *)(object));
}static void 
gst_qnxaudio_sink_set_property(GObject *object, guint prop_id,const GValue *value, GParamSpec *pspec)
{/** 设置属性 *///printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);GstQnxAudioSink *sink;sink = GST_QNXAUDIOSINK(object);switch (prop_id){case PROP_DEVICE://printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);g_free(sink->device);sink->device = g_value_dup_string(value);if (sink->probed_caps){gst_caps_unref(sink->probed_caps);sink->probed_caps = NULL;}break;default:G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);break;}
}static void gst_qnxaudio_sink_get_property(GObject *object, guint prop_id,GValue *value, GParamSpec *pspec)
{GstQnxAudioSink *sink;//printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);sink = GST_QNXAUDIOSINK(object);switch (prop_id){case PROP_DEVICE:g_value_set_string(value, sink->device);break;default:G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);break;}
}static GstCaps *gst_qnxaudio_sink_getcaps(GstBaseSink *bsink, GstCaps *filter)
{GstQnxAudioSink *qnxaudio;    GstCaps *caps;qnxaudio = GST_QNXAUDIOSINK(bsink);// printf("[%s.%d]===>:pcm_handle: %p\n", // __FUNCTION__, __LINE__, qnxaudio->pcm_handle);if (qnxaudio->pcm_handle == NULL){////printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);caps = gst_pad_get_pad_template_caps(GST_BASE_SINK_PAD(bsink));}else if (qnxaudio->probed_caps){////printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);caps = gst_caps_ref(qnxaudio->probed_caps);}else{//printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);caps = gst_qnxaudio_helper_probe_caps(&qnxaudio->channelInfo);if (caps && !gst_caps_is_empty(caps)){qnxaudio->probed_caps = gst_caps_ref(caps);}}if (filter && caps){//printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);GstCaps *intersection;intersection =gst_caps_intersect_full(filter, caps, GST_CAPS_INTERSECT_FIRST);gst_caps_unref(caps);return intersection;}else{////printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return caps;}
}static gint ilog2(gint x)
{/* well... hacker's delight explains... */x = x | (x >> 1);x = x | (x >> 2);x = x | (x >> 4);x = x | (x >> 8);x = x | (x >> 16);x = x - ((x >> 1) & 0x55555555);x = (x & 0x33333333) + ((x >> 2) & 0x33333333);x = (x + (x >> 4)) & 0x0f0f0f0f;x = x + (x >> 8);x = x + (x >> 16);return (x & 0x0000003f) - 1;
}static gint 
gst_qnxaudio_sink_get_format(GstAudioRingBufferFormatType fmt, GstAudioFormat rfmt)
{gint result = -1;switch (fmt){case GST_AUDIO_RING_BUFFER_FORMAT_TYPE_MU_LAW:result = SND_PCM_SFMT_MU_LAW;break;case GST_AUDIO_RING_BUFFER_FORMAT_TYPE_A_LAW:result = SND_PCM_SFMT_A_LAW;break;case GST_AUDIO_RING_BUFFER_FORMAT_TYPE_IMA_ADPCM:result = SND_PCM_SFMT_IMA_ADPCM;break;case GST_AUDIO_RING_BUFFER_FORMAT_TYPE_MPEG:result = SND_PCM_SFMT_MPEG;break;case GST_AUDIO_RING_BUFFER_FORMAT_TYPE_RAW:{switch (rfmt){case GST_AUDIO_FORMAT_U8:result = SND_PCM_SFMT_U8;break;case GST_AUDIO_FORMAT_S16LE:result = SND_PCM_SFMT_S16_LE;break;case GST_AUDIO_FORMAT_S16BE:result = SND_PCM_SFMT_S16_BE;break;case GST_AUDIO_FORMAT_S8:result = SND_PCM_SFMT_S8;break;case GST_AUDIO_FORMAT_U16LE:result = SND_PCM_SFMT_U16_LE;break;case GST_AUDIO_FORMAT_U16BE:result = SND_PCM_SFMT_U16_BE;break;default:result = -1;break;}break;}default:result = -1;break;}return result;
}static gboolean gst_qnxaudio_sink_open(GstAudioSink *asink)
{//printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);GstQnxAudioSink *qnxaudio;qnxaudio = GST_QNXAUDIOSINK(asink);int rtn = snd_pcm_open_name(&qnxaudio->pcm_handle, qnxaudio->device, SND_PCM_OPEN_PLAYBACK);if (rtn == EOK){rtn = snd_pcm_info(qnxaudio->pcm_handle, &qnxaudio->info);if (rtn == 0){qnxaudio->channelInfo.channel = SND_PCM_CHANNEL_PLAYBACK;rtn = snd_pcm_plugin_info(qnxaudio->pcm_handle, &qnxaudio->channelInfo);if (rtn == 0){qnxaudio->audioCard = qnxaudio->info.card;//printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return TRUE;}else{GST_ELEMENT_ERROR(qnxaudio, RESOURCE, OPEN_WRITE, (NULL),("Could not open audio device for playback." "snd_pcm_plugin_info failed: %s\n", snd_strerror(rtn)));}/** todo something */}else{GST_ELEMENT_ERROR(qnxaudio, RESOURCE, OPEN_WRITE,(("Could not open audio device for playback. ""get qnx audio pcm info failedd")),(NULL));}rtn = snd_pcm_close(qnxaudio->pcm_handle);}else{GST_ERROR_OBJECT(qnxaudio, "open qnx audio output device: %s failed\n", qnxaudio->device);/** Errors */if (rtn == -EINVAL){GST_ELEMENT_ERROR(qnxaudio, RESOURCE, OPEN_WRITE,(("Could not open audio device for playback. ""The mode is invalid")),(NULL));}else if (rtn == -ENOENT){GST_ELEMENT_ERROR(qnxaudio, RESOURCE, NOT_FOUND,(("Could not open audio device for playback. ""The named device doesn't exist.")),(NULL));}else if (rtn == -ENOMEM){GST_ELEMENT_ERROR(qnxaudio, RESOURCE, NO_SPACE_LEFT,(("Could not open audio device for playback. ""Not enough memory is available to allocate the""control structures")),(NULL));}else if (rtn == -SND_ERROR_INCOMPATIBLE_VERSION){GST_ELEMENT_ERROR(qnxaudio, RESOURCE, OPEN_WRITE,(("Could not open audio device for playback. ""The audio driver version is incompatible ""with the client library that the application""is using.")),(NULL));}}qnxaudio->pcm_handle = NULL;qnxaudio->mixer_handle = NULL;//printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return FALSE;
}static gboolean gst_qnxaudio_sink_close(GstAudioSink *asink)
{GstQnxAudioSink *qnxaudio;int rtn;qnxaudio = GST_QNXAUDIOSINK(asink);//printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);if (qnxaudio->pcm_handle){rtn = snd_pcm_plugin_flush(qnxaudio->pcm_handle, SND_PCM_CHANNEL_PLAYBACK);       }if (qnxaudio->mixer_handle){rtn = snd_mixer_close(qnxaudio->mixer_handle);if (rtn != 0){GST_ERROR_OBJECT(qnxaudio, "close mixer failed: %d\n", rtn);return FALSE;}  qnxaudio->mixer_handle = NULL;      }if (qnxaudio->pcm_handle){rtn = snd_pcm_close(qnxaudio->pcm_handle);if (rtn != 0){GST_ERROR_OBJECT(qnxaudio, "close qnx audio device failed: %d\n", rtn);return FALSE;}qnxaudio->pcm_handle = NULL;        }//printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return TRUE;
}static gboolean 
gst_qnxaudio_sink_prepare(GstAudioSink *asink, GstAudioRingBufferSpec *spec)
{GstQnxAudioSink *qnxaudio;int tmp;guint mSampleBits, mSampleRate, mSampleChannels;gint fragSize;snd_pcm_channel_params_t* pChParam;qnxaudio = GST_QNXAUDIOSINK(asink);//printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);tmp = gst_qnxaudio_sink_get_format(spec->type,GST_AUDIO_INFO_FORMAT(&spec->info));if (tmp == -1){GST_ELEMENT_ERROR(qnxaudio, RESOURCE, SETTINGS, (NULL),("Unable to get format (%d, %d)", spec->type,GST_AUDIO_INFO_FORMAT(&spec->info)));return FALSE;}mSampleBits = GST_AUDIO_INFO_WIDTH(&spec->info);mSampleRate = GST_AUDIO_INFO_RATE(&spec->info);mSampleChannels = GST_AUDIO_INFO_CHANNELS(&spec->info);if (mSampleBits != 16 && mSampleBits != 8){GST_ELEMENT_ERROR(qnxaudio, RESOURCE, SETTINGS, (NULL),("unexpected width %d", mSampleBits));return FALSE;}tmp = ilog2(spec->segsize);tmp = ((spec->segtotal & 0x7fff) << 16) | tmp;GST_DEBUG_OBJECT(qnxaudio, "set segsize: %d, segtotal: %d, value: %08x",spec->segsize, spec->segtotal, tmp);fragSize = 0;pChParam = &qnxaudio->channelParam;pChParam->mode = SND_PCM_MODE_BLOCK;pChParam->channel = SND_PCM_CHANNEL_PLAYBACK;pChParam->start_mode = SND_PCM_START_FULL;pChParam->stop_mode = SND_PCM_STOP_STOP;pChParam->buf.block.frag_size = qnxaudio->channelInfo.max_fragment_size;if (fragSize != -1){pChParam->buf.block.frag_size = fragSize;}pChParam->buf.block.frags_max = -1; //num_frags;pChParam->buf.block.frags_min = 1;pChParam->format.interleave = 1;pChParam->format.rate = mSampleRate;pChParam->format.voices = mSampleChannels;if (mSampleBits == 8){pChParam->format.format = SND_PCM_SFMT_U8;}else if (mSampleBits == 16){pChParam->format.format = SND_PCM_SFMT_S16_LE;}else{pChParam->format.format = SND_PCM_SFMT_S16_LE;}strcpy(pChParam->sw_mixer_subchn_name, "Wave playback channel");tmp = snd_pcm_plugin_params(qnxaudio->pcm_handle, &qnxaudio->channelParam);if (tmp < 0){GST_ELEMENT_ERROR(qnxaudio, RESOURCE, SETTINGS, (NULL),("snd_pcm_plugin_params failed: %s\n",snd_strerror(tmp)));return FALSE;}tmp = snd_pcm_plugin_prepare(qnxaudio->pcm_handle, SND_PCM_CHANNEL_PLAYBACK);if (tmp < 0){GST_ELEMENT_ERROR(qnxaudio, RESOURCE, SETTINGS, (NULL),("snd_pcm_plugin_prepare failed: %s\n",snd_strerror(tmp)));return FALSE;}qnxaudio->channelSetup.channel = SND_PCM_CHANNEL_PLAYBACK;qnxaudio->channelSetup.mixer_gid = &qnxaudio->mixerGroup.gid;tmp = snd_pcm_plugin_setup(qnxaudio->pcm_handle, &qnxaudio->channelSetup);if (tmp < 0){GST_ELEMENT_ERROR(qnxaudio, RESOURCE, SETTINGS, (NULL),("snd_pcm_plugin_setup failed: %s\n",snd_strerror(tmp)));return FALSE;}GST_INFO_OBJECT(qnxaudio, "Format %s \n", snd_pcm_get_format_name(qnxaudio->channelSetup.format.format));GST_INFO_OBJECT(qnxaudio, "Frag Size %d \n", qnxaudio->channelSetup.buf.block.frag_size);GST_INFO_OBJECT(qnxaudio, "Total Frags %d \n", qnxaudio->channelSetup.buf.block.frags);GST_INFO_OBJECT(qnxaudio, "Rate %d \n", qnxaudio->channelSetup.format.rate);GST_INFO_OBJECT(qnxaudio, "Voices %d \n", qnxaudio->channelSetup.format.voices);if (qnxaudio->mixerGroup.gid.name[0] == 0){GST_ELEMENT_ERROR(qnxaudio, RESOURCE, SETTINGS, (NULL),("Mixer Pcm Group [%s] Not Set \n",qnxaudio->mixerGroup.gid.name));return FALSE;}tmp = snd_mixer_open(&qnxaudio->mixer_handle, qnxaudio->audioCard, qnxaudio->channelSetup.mixer_device);if (tmp < 0){GST_ELEMENT_ERROR(qnxaudio, RESOURCE, SETTINGS, (NULL),("snd_mixer_open failed: %s\n",snd_strerror(tmp)));return FALSE;}spec->segsize = pChParam->buf.block.frag_size;//spec->segtotal = info.fragstotal;qnxaudio->bytes_per_sample = GST_AUDIO_INFO_BPF(&spec->info);GST_DEBUG_OBJECT(qnxaudio, "got segsize: %d, segtotal: %d, value: %08x",spec->segsize, spec->segtotal, tmp);//printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return TRUE;
}static gboolean gst_qnxaudio_sink_unprepare(GstAudioSink *asink)
{//printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);if (!gst_qnxaudio_sink_close(asink)){GST_ERROR_OBJECT(asink, "Could not close the audio device");return FALSE;}if (!gst_qnxaudio_sink_open(asink)){GST_ERROR_OBJECT(asink, "Could not reopen the audio device");return FALSE;}//printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return TRUE;
}static gint gst_qnxaudio_sink_write(GstAudioSink *asink, gpointer data, guint length)
{////printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return snd_pcm_plugin_write(GST_QNXAUDIOSINK(asink)->pcm_handle, data, length);
}static guint gst_qnxaudio_sink_delay(GstAudioSink *asink)
{GstQnxAudioSink *qnxaudio;////printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);snd_pcm_channel_status_t status;memset(&status, 0, sizeof(status));status.channel = SND_PCM_CHANNEL_PLAYBACK;qnxaudio = GST_QNXAUDIOSINK(asink);if (snd_pcm_plugin_status(qnxaudio->pcm_handle, &status) < 0){GST_ERROR_OBJECT(asink, "underrun: playback channel status error\n");return 0;}return status.count / qnxaudio->bytes_per_sample;
}static void gst_qnxaudio_sink_reset(GstAudioSink *asink)
{//printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);/* There's nothing we can do here really, * 对于qnx audio这里没有实现这个接口 **/
}//////////////////////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////////////////////GST_DEBUG_CATEGORY (qnxaudio_debug);
#define GST_CAT_DEFAULT qnxaudio_debugstatic gboolean
plugin_init (GstPlugin * plugin)
{//printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);/** 注册 qnxaudiosink这个元件 */if (!gst_element_register(plugin, "qnxaudiosink", GST_RANK_SECONDARY,GST_TYPE_QNXAUDIOSINK)){return FALSE;}GST_DEBUG_CATEGORY_INIT(qnxaudio_debug, "qnxaudio",0, "QNX audio elements");#ifdef ENABLE_NLSGST_DEBUG("binding text domain %s to locale dir %s", GETTEXT_PACKAGE,LOCALEDIR);bindtextdomain(GETTEXT_PACKAGE, LOCALEDIR);bind_textdomain_codeset(GETTEXT_PACKAGE, "UTF-8");
#endif /* ENABLE_NLS *///printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return TRUE;
}GST_PLUGIN_DEFINE (GST_VERSION_MAJOR,GST_VERSION_MINOR,qnxaudio,"Qnx Audio support for GStreamer",plugin_init, PLUGIN_VERSION, GST_LICENSE, GST_PACKAGE_NAME, GST_PACKAGE_ORIGIN)

三、 实现QNX video sink 插件

和audio sink一样，gstreamer也提供了video sink的“基类”GstVideoSinkClass， 其内容就相对比较简单：

/*** GstVideoSinkClass:* @parent_class: the parent class structure* @show_frame: render a video frame. Maps to #GstBaseSinkClass.render() and*     #GstBaseSinkClass.preroll() vfuncs. Rendering during preroll will be*     suppressed if the #GstVideoSink:show-preroll-frame property is set to*     %FALSE.** The video sink class structure. Derived classes should override the* @show_frame virtual function.*/
struct _GstVideoSinkClass {GstBaseSinkClass parent_class;GstFlowReturn  (*show_frame) (GstVideoSink *video_sink, GstBuffer *buf);/*< private >*/gpointer _gst_reserved[GST_PADDING];
};

一样的参考现有的视频输出元件的模板，定义头文件如下：

/* GStreamer* Copyright (C) gu.wen <454727014@qq.com>** gstqnxvideosink.h: **/#ifndef __GST_QNX_VIDEO_SINK_H__
#define __GST_QNX_VIDEO_SINK_H__#include <gst/gst.h>
#include <gst/video/video.h>
#include <gst/video/gstvideosink.h>//for qnx screen api
#include <screen/screen.h>//#include <aalib.h>#ifdef __cplusplus
extern "C"
{
#endif /* __cplusplus */#define GST_TYPE_QNXVIDEOSINK \(gst_qnxvideo_sink_get_type())
#define GST_QNXVIDEOSINK(obj) \(G_TYPE_CHECK_INSTANCE_CAST((obj), GST_TYPE_QNXVIDEOSINK, GstQnxVideoSink))
#define GST_QNXVIDEOSINK_CLASS(klass) \(G_TYPE_CHECK_CLASS_CAST((klass), GST_TYPE_QNXVIDEOSINK, GstQnxVideoSinkClass))
#define GST_IS_QNXVIDEOSINK(obj) \(G_TYPE_CHECK_INSTANCE_TYPE((obj), GST_TYPE_QNXVIDEOSINK))
#define GST_IS_QNXVIDEOSINK_CLASS(klass) \(G_TYPE_CHECK_CLASS_TYPE((klass), GST_TYPE_QNXVIDEOSINK))typedef struct _GstQnxVideoSink GstQnxVideoSink;typedef struct _GstQnxVideoSinkClass GstQnxVideoSinkClass;struct _GstQnxVideoSink
{/** qnx video sink 继承 自  GstVideoSink */GstVideoSink parent;GstVideoInfo info;gint frames_displayed;guint64 frame_time;screen_context_t screen_ctx;screen_window_t screen_win;gboolean isOpened;screen_buffer_t dispBuf[2];gint dispRect[4]; /** dsiaply rect size */gint startX;gint startY;gint width;gint height;
};struct _GstQnxVideoSinkClass
{/** qnx video sink class 继承自 GstVideoSinkClass */GstVideoSinkClass parent_class;
};GType gst_qnxvideo_sink_get_type(void);#ifdef __cplusplus
}
#endif /* __cplusplus */#endif /* __GST_QNXVIDEOSINKE_H__ */

接下来就是重点，具体的video sink元件的实现,其代码稍微有点多，具体如下所示。

/* GStreamer* Copyright (C) gu.wen <454727014@qq.com>** gstqnxvideosink.c: **//*** SECTION:element-qnxvideosink* @see_also: #GstQnxVideoSink** Displays video on qnx.** <refsect2>* <title>Example launch line</title>* |[* gst-launch-1.0 filesrc location=test.avi ! decodebin ! videoconvert * ! qnxvideosink ]| This pipeline renders a video to ascii art into*  a separate window. |[* gst-launch-1.0 filesrc location=test.avi ! decodebin ! videoconvert * ! qnxvideosink driver=curses ]| * This pipeline renders a video to ascii art into the current terminal.* </refsect2>*/#ifdef HAVE_CONFIG_H
#include "config.h"
#endif#include <string.h>
#include <sys/time.h>#include <gst/video/gstvideometa.h>
#include "gstQnxVideoSink.h"///////////////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////////////#define PLUGIN_VERSION "00.01.00"
#define PACKAGE "gst-plugins-qnx"
#define GST_LICENSE "LGPL"
#define GST_PACKAGE_NAME "GStreamer qnx Plug-ins source release"
#define GST_PACKAGE_ORIGIN "Unknown package origin"#define GST_DEFAULT_FRAME_BUF_CNT 4
#define GST_DISP_BUF_CNT 4
#define GST_DISP_USAGE SCREEN_USAGE_NATIVE|SCREEN_USAGE_WRITE
/* qnxvideosink signals and args */
enum
{LAST_SIGNAL
};enum
{PROP_0,PROP_WIDTH,PROP_HEIGHT,
#if 0PROP_DRIVER,PROP_DITHER,PROP_BRIGHTNESS,PROP_CONTRAST,PROP_GAMMA,PROP_INVERSION,PROP_RANDOMVAL,
#endifPROP_FRAMES_DISPLAYED,PROP_FRAME_TIME
};static GstStaticPadTemplate sink_template = GST_STATIC_PAD_TEMPLATE("sink", GST_PAD_SINK,GST_PAD_ALWAYS,GST_STATIC_CAPS(GST_VIDEO_CAPS_MAKE("NV12")));static GstCaps *gst_qnxvideo_sink_fixate(GstBaseSink *bsink, GstCaps *caps);
static gboolean gst_qnxvideo_sink_setcaps(GstBaseSink *bsink, GstCaps *caps);
static void gst_qnxvideo_sink_get_times(GstBaseSink *bsink, GstBuffer *buffer,GstClockTime *start, GstClockTime *end);static gboolean gst_qnxvideo_sink_propose_allocation(GstBaseSink *bsink,GstQuery *query);
static GstFlowReturn gst_qnxvideo_sink_show_frame(GstVideoSink *videosink,GstBuffer *buffer);static void gst_qnxvideo_sink_set_property(GObject *object, guint prop_id,const GValue *value, GParamSpec *pspec);static void gst_qnxvideo_sink_get_property(GObject *object, guint prop_id,GValue *value, GParamSpec *pspec);static GstStateChangeReturn gst_qnxvideo_sink_change_state(GstElement *element,GstStateChange transition);#define gst_qnxvideo_sink_parent_class parent_class
G_DEFINE_TYPE(GstQnxVideoSink, gst_qnxvideo_sink, GST_TYPE_VIDEO_SINK);#if 0
#define GST_TYPE_QNXVIDEODRIVERS (gst_qnxvideo_sink_drivers_get_type())
static GType gst_qnxvideo_sink_drivers_get_type(void)
{static GType driver_type = 0;if (!driver_type){GEnumValue *drivers;const struct aa_driver *driver;gint n_drivers;gint i;for (n_drivers = 0; aa_drivers[n_drivers]; n_drivers++){/* count number of drivers */}drivers = g_new0(GEnumValue, n_drivers + 1);for (i = 0; i < n_drivers; i++){driver = aa_drivers[i];drivers[i].value = i;drivers[i].value_name = g_strdup(driver->name);drivers[i].value_nick = g_utf8_strdown(driver->shortname, -1);}drivers[i].value = 0;drivers[i].value_name = NULL;drivers[i].value_nick = NULL;driver_type = g_enum_register_static("GstQnxVideoSinkDrivers", drivers);}return driver_type;
}#define GST_TYPE_AADITHER (gst_qnxvideo_sink_dither_get_type())
static GType gst_qnxvideo_sink_dither_get_type(void)
{static GType dither_type = 0;if (!dither_type){GEnumValue *ditherers;gint n_ditherers;gint i;for (n_ditherers = 0; aa_dithernames[n_ditherers]; n_ditherers++){/* count number of ditherers */}ditherers = g_new0(GEnumValue, n_ditherers + 1);for (i = 0; i < n_ditherers; i++){ditherers[i].value = i;ditherers[i].value_name = g_strdup(aa_dithernames[i]);ditherers[i].value_nick =g_strdelimit(g_strdup(aa_dithernames[i]), " _", '-');}ditherers[i].value = 0;ditherers[i].value_name = NULL;ditherers[i].value_nick = NULL;dither_type = g_enum_register_static("GstQnxVideoSinkDitherers", ditherers);}return dither_type;
}
#endifstatic void gst_qnxvideo_sink_class_init(GstQnxVideoSinkClass *klass)
{GObjectClass *gobject_class;GstElementClass *gstelement_class;GstBaseSinkClass *gstbasesink_class;GstVideoSinkClass *gstvideosink_class;printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);gobject_class = (GObjectClass *)klass;gstelement_class = (GstElementClass *)klass;gstbasesink_class = (GstBaseSinkClass *)klass;gstvideosink_class = (GstVideoSinkClass *)klass;gobject_class->set_property = gst_qnxvideo_sink_set_property;gobject_class->get_property = gst_qnxvideo_sink_get_property;/* FIXME: add long property descriptions */g_object_class_install_property(G_OBJECT_CLASS(klass), PROP_WIDTH,g_param_spec_int("width", "width", "width", G_MININT, G_MAXINT, 0,G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));g_object_class_install_property(G_OBJECT_CLASS(klass), PROP_HEIGHT,g_param_spec_int("height", "height", "height", G_MININT, G_MAXINT, 0,G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));
#if 0  g_object_class_install_property (G_OBJECT_CLASS (klass), PROP_DRIVER,g_param_spec_enum ("driver", "driver", "driver", GST_TYPE_QNXVIDEODRIVERS, 0, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));g_object_class_install_property (G_OBJECT_CLASS (klass), PROP_DITHER,g_param_spec_enum ("dither", "dither", "dither", GST_TYPE_AADITHER, 0,G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));g_object_class_install_property (G_OBJECT_CLASS (klass), PROP_BRIGHTNESS,g_param_spec_int ("brightness", "brightness", "brightness", G_MININT,G_MAXINT, 0, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));g_object_class_install_property (G_OBJECT_CLASS (klass), PROP_CONTRAST,g_param_spec_int ("contrast", "contrast", "contrast", G_MININT, G_MAXINT,0, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));g_object_class_install_property (G_OBJECT_CLASS (klass), PROP_GAMMA,g_param_spec_float ("gamma", "gamma", "gamma", 0.0, 5.0, 1.0,G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));g_object_class_install_property (G_OBJECT_CLASS (klass), PROP_INVERSION,g_param_spec_boolean ("inversion", "inversion", "inversion", TRUE,G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));g_object_class_install_property (G_OBJECT_CLASS (klass), PROP_RANDOMVAL,g_param_spec_int ("randomval", "randomval", "randomval", G_MININT,G_MAXINT, 0, G_PARAM_READWRITE | G_PARAM_STATIC_STRINGS));g_object_class_install_property(G_OBJECT_CLASS(klass),PROP_FRAMES_DISPLAYED, g_param_spec_int("frames-displayed", "frames displayed", "frames displayed", G_MININT, G_MAXINT, 0, G_PARAM_READABLE |G_PARAM_STATIC_STRINGS));g_object_class_install_property(G_OBJECT_CLASS(klass), PROP_FRAME_TIME,g_param_spec_int("frame-time", "frame time", "frame time", G_MININT,G_MAXINT, 0, G_PARAM_READABLE |G_PARAM_STATIC_STRINGS));
#endifgst_element_class_add_static_pad_template(gstelement_class, &sink_template);gst_element_class_set_static_metadata(gstelement_class,"Qnx video sink", "Sink/Video", "An Qnx videosink","guwen <454727014@qq.com>");gstelement_class->change_state = GST_DEBUG_FUNCPTR(gst_qnxvideo_sink_change_state);gstbasesink_class->fixate = GST_DEBUG_FUNCPTR(gst_qnxvideo_sink_fixate);gstbasesink_class->set_caps = GST_DEBUG_FUNCPTR(gst_qnxvideo_sink_setcaps);gstbasesink_class->get_times = GST_DEBUG_FUNCPTR(gst_qnxvideo_sink_get_times);gstbasesink_class->propose_allocation =GST_DEBUG_FUNCPTR(gst_qnxvideo_sink_propose_allocation);gstvideosink_class->show_frame = GST_DEBUG_FUNCPTR(gst_qnxvideo_sink_show_frame);printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);
}static GstCaps* gst_qnxvideo_sink_fixate(GstBaseSink *bsink, GstCaps *caps)
{GstStructure *structure;printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);caps = gst_caps_make_writable(caps);structure = gst_caps_get_structure(caps, 0);gst_structure_fixate_field_nearest_int(structure, "width", 1920);gst_structure_fixate_field_nearest_int(structure, "height", 720);gst_structure_fixate_field_nearest_fraction(structure, "framerate", 30, 1);caps = GST_BASE_SINK_CLASS(parent_class)->fixate(bsink, caps);printf("[%s.%d]===>:caps: %p\n", __FUNCTION__, __LINE__, caps);return caps;
}static gboolean gst_qnxvideo_sink_setcaps(GstBaseSink *basesink, GstCaps *caps)
{GstQnxVideoSink *qnxvideosink;GstVideoInfo info;printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);qnxvideosink = GST_QNXVIDEOSINK(basesink);if (!gst_video_info_from_caps(&info, caps))goto invalid_caps;qnxvideosink->info = info;qnxvideosink->width = info.width;qnxvideosink->height = info.height;printf("[%s.%d]===>:witdh: %d, height:%d\n", __FUNCTION__, __LINE__, info.width, info.height);if (qnxvideosink->screen_win){memset(&(qnxvideosink->dispRect), 0, sizeof(qnxvideosink->dispRect));qnxvideosink->dispRect[2] = qnxvideosink->width;qnxvideosink->dispRect[3] = qnxvideosink->height;screen_create_window_buffers(qnxvideosink->screen_win, GST_DISP_BUF_CNT);//screen_get_window_property_iv(qnxvideosink->screen_win,//                              SCREEN_PROPERTY_BUFFER_SIZE,//                              qnxvideosink->dispRect + 2);screen_set_window_property_iv(qnxvideosink->screen_win, SCREEN_PROPERTY_SIZE, qnxvideosink->dispRect + 2);screen_set_window_property_iv(qnxvideosink->screen_win, SCREEN_PROPERTY_BUFFER_SIZE, qnxvideosink->dispRect + 2);}printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return TRUE;/* ERRORS */
invalid_caps:
{GST_ERROR_OBJECT(qnxvideosink, "invalid caps");printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return FALSE;
}
}static void
gst_qnxvideo_sink_init(GstQnxVideoSink *qnxvideosink)
{
#if 0    memcpy(&qnxvideosink->ascii_surf, &aa_defparams,sizeof(struct aa_hardware_params));qnxvideosink->ascii_parms.bright = 0;qnxvideosink->ascii_parms.contrast = 16;qnxvideosink->ascii_parms.gamma = 1.0;qnxvideosink->ascii_parms.dither = 0;qnxvideosink->ascii_parms.inversion = 0;qnxvideosink->ascii_parms.randomval = 0;qnxvideosink->aa_driver = 0;
#elseprintf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);qnxvideosink->screen_win = NULL;qnxvideosink->screen_ctx = NULL;qnxvideosink->isOpened = FALSE;memset(&(qnxvideosink->dispRect), 0, sizeof(qnxvideosink->dispRect));printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);
#endif
}static void gst_qnxvideo_sink_scale(GstQnxVideoSink *qnxvideosink, guchar *src, guchar *dest,gint sw, gint sh, gint ss, gint dw, gint dh)
{gint ypos, yinc, y;gint xpos, xinc, x;g_return_if_fail((dw != 0) && (dh != 0));ypos = 0x10000;yinc = (sh << 16) / dh;xinc = (sw << 16) / dw;for (y = dh; y; y--){while (ypos > 0x10000){ypos -= 0x10000;src += ss;}xpos = 0x10000;{guchar *destp = dest;guchar *srcp = src;for (x = dw; x; x--){while (xpos >= 0x10000L){srcp++;xpos -= 0x10000L;}*destp++ = *srcp;xpos += xinc;}}dest += dw;ypos += yinc;}
}static void
gst_qnxvideo_sink_get_times(GstBaseSink *sink, GstBuffer *buffer,GstClockTime *start, GstClockTime *end)
{//printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);*start = GST_BUFFER_TIMESTAMP(buffer);if (GST_BUFFER_DURATION_IS_VALID(buffer))*end = *start + GST_BUFFER_DURATION(buffer);
}static gboolean gst_qnxvideo_sink_propose_allocation(GstBaseSink *bsink, GstQuery *query)
{GstCaps *caps;GstVideoInfo info;guint size;printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);gst_query_parse_allocation(query, &caps, NULL);if (caps == NULL)goto no_caps;if (!gst_video_info_from_caps(&info, caps))goto invalid_caps;size = GST_VIDEO_INFO_SIZE(&info);/* we need at least 2 buffer because we hold on to the last one */gst_query_add_allocation_pool(query, NULL, size, GST_DEFAULT_FRAME_BUF_CNT, 0);/* we support various metadata */gst_query_add_allocation_meta(query, GST_VIDEO_META_API_TYPE, NULL);printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return TRUE;/* ERRORS */
no_caps:
{GST_ERROR_OBJECT(bsink, "no caps specified");printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return FALSE;
}
invalid_caps:
{GST_ERROR_OBJECT(bsink, "invalid caps specified");printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return FALSE;
}
}static GstFlowReturn gst_qnxvideo_sink_show_frame(GstVideoSink *videosink, GstBuffer *buffer)
{GstQnxVideoSink *qnxvideosink;GstVideoFrame frame;//  printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);qnxvideosink = GST_QNXVIDEOSINK(videosink);GST_DEBUG("show frame");if (!gst_video_frame_map(&frame, &qnxvideosink->info, buffer, GST_MAP_READ))goto invalid_frame;#if 0screen_pixmap_t pixmapInfo;screen_create_pixmap(&pixmapInfo, qnxvideosink->screen_ctx);int format = SCREEN_FORMAT_NV12;screen_set_pixmap_property_iv(pixmapInfo, SCREEN_PROPERTY_FORMAT, &format);gint usage = SCREEN_USAGE_WRITE | SCREEN_USAGE_NATIVE;screen_set_pixmap_property_iv(pixmapInfo, SCREEN_PROPERTY_USAGE, &usage);int size[2] = { qnxvideosink->width, qnxvideosink->height };screen_set_pixmap_property_iv(pixmapInfo, SCREEN_PROPERTY_BUFFER_SIZE, size);screen_buffer_t pixmapBuf;screen_create_pixmap_buffer(pixmapInfo);screen_get_pixmap_property_pv(pixmapInfo, SCREEN_PROPERTY_RENDER_BUFFERS, (void **)&pixmapBuf);unsigned char *pBuf = NULL;screen_get_buffer_property_pv(pixmapBuf, SCREEN_PROPERTY_POINTER, (void **)&pBuf);int stride = 0;screen_get_buffer_property_iv(pixmapBuf, SCREEN_PROPERTY_STRIDE, &stride);
#if 0for (i = 0; i < size[1]; i++, ptr += stride) {for (j = 0; j < size[0]; j++) {ptr[j*4] = 0xa0;ptr[j*4+1] = 0xa0;ptr[j*4+2] = 0xa0;ptr[j*4+3] = ((j >= i && j <= size[1]-i) || (j <= i && j >= size[1]-i)) ? 0xff : 0;}}
#endif#if 0gst_qnxvideo_sink_scale(qnxvideosink, GST_VIDEO_FRAME_PLANE_DATA(&frame, 0), /* src */pBuf,                     /* dest */GST_VIDEO_INFO_WIDTH(&qnxvideosink->info),  /* sw */GST_VIDEO_INFO_HEIGHT(&qnxvideosink->info), /* sh */GST_VIDEO_FRAME_PLANE_STRIDE(&frame, 0),    /* ss */qnxvideosink->width,                  /* dw */qnxvideosink->height);                /* dh */#elsememcpy(pBuf, GST_VIDEO_FRAME_PLANE_DATA(&frame, 0), qnxvideosink->width * qnxvideosink->height * 3 / 2);
#endifscreen_buffer_t render_buf[2];screen_get_window_property_pv(qnxvideosink->screen_win, SCREEN_PROPERTY_RENDER_BUFFERS, (void **)render_buf);int hg[] = {SCREEN_BLIT_SOURCE_WIDTH, qnxvideosink->width,SCREEN_BLIT_SOURCE_HEIGHT, qnxvideosink->height,SCREEN_BLIT_DESTINATION_X, 0,SCREEN_BLIT_DESTINATION_Y, 0,SCREEN_BLIT_DESTINATION_WIDTH, qnxvideosink->width,SCREEN_BLIT_DESTINATION_HEIGHT, qnxvideosink->height,SCREEN_BLIT_TRANSPARENCY, SCREEN_TRANSPARENCY_SOURCE_OVER,SCREEN_BLIT_END};screen_blit(qnxvideosink->screen_ctx, render_buf[0], pixmapBuf, hg);screen_post_window(qnxvideosink->screen_win, render_buf[0], 1, qnxvideosink->dispRect, 0);    screen_destroy_pixmap(pixmapInfo);
#elsescreen_buffer_t render_buf[GST_DISP_BUF_CNT];screen_get_window_property_pv(qnxvideosink->screen_win, SCREEN_PROPERTY_RENDER_BUFFERS, (void **)&render_buf);   char *pBuf = NULL;screen_get_buffer_property_pv(render_buf[0], SCREEN_PROPERTY_POINTER, (void **)&pBuf); memcpy(pBuf, GST_VIDEO_FRAME_PLANE_DATA(&frame, 0), qnxvideosink->width * qnxvideosink->height * 3 / 2);screen_post_window(qnxvideosink->screen_win, render_buf[0], 1, qnxvideosink->dispRect, 0);
#endifgst_video_frame_unmap(&frame);qnxvideosink->frames_displayed++;//  printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return GST_FLOW_OK;/* ERRORS */
invalid_frame:
{GST_ERROR_OBJECT(qnxvideosink, "invalid frame");printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return GST_FLOW_ERROR;
}
}static void
gst_qnxvideo_sink_set_property(GObject *object, guint prop_id, const GValue *value,GParamSpec *pspec)
{GstQnxVideoSink *qnxvideosink;printf("[%s.%d]===>: prop_id:%d\n", __FUNCTION__, __LINE__, prop_id);qnxvideosink = GST_QNXVIDEOSINK(object);switch (prop_id){case PROP_WIDTH:qnxvideosink->width = g_value_get_int(value);break;case PROP_HEIGHT:qnxvideosink->height = g_value_get_int(value);break;
#if 0case PROP_DRIVER:{qnxvideosink->aa_driver = g_value_get_enum(value);break;}case PROP_DITHER:{qnxvideosink->ascii_parms.dither = g_value_get_enum(value);break;}case PROP_BRIGHTNESS:{qnxvideosink->ascii_parms.bright = g_value_get_int(value);break;}case PROP_CONTRAST:{qnxvideosink->ascii_parms.contrast = g_value_get_int(value);break;}case PROP_GAMMA:{qnxvideosink->ascii_parms.gamma = g_value_get_float(value);break;}case PROP_INVERSION:{qnxvideosink->ascii_parms.inversion = g_value_get_boolean(value);break;}case PROP_RANDOMVAL:{qnxvideosink->ascii_parms.randomval = g_value_get_int(value);break;}
#endifdefault:break;}printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);
}static void
gst_qnxvideo_sink_get_property(GObject *object, guint prop_id, GValue *value,GParamSpec *pspec)
{GstQnxVideoSink *qnxvideosink;printf("[%s.%d]===>:, prop_id: %d\n", __FUNCTION__, __LINE__, prop_id);qnxvideosink = GST_QNXVIDEOSINK(object);switch (prop_id){case PROP_WIDTH:{g_value_set_int(value, qnxvideosink->width);break;}case PROP_HEIGHT:{g_value_set_int(value, qnxvideosink->height);break;}
#if 0case PROP_DRIVER:{g_value_set_enum(value, qnxvideosink->aa_driver);break;}case PROP_DITHER:{g_value_set_enum(value, qnxvideosink->ascii_parms.dither);break;}case PROP_BRIGHTNESS:{g_value_set_int(value, qnxvideosink->ascii_parms.bright);break;}case PROP_CONTRAST:{g_value_set_int(value, qnxvideosink->ascii_parms.contrast);break;}case PROP_GAMMA:{g_value_set_float(value, qnxvideosink->ascii_parms.gamma);break;}case PROP_INVERSION:{g_value_set_boolean(value, qnxvideosink->ascii_parms.inversion);break;}case PROP_RANDOMVAL:{g_value_set_int(value, qnxvideosink->ascii_parms.randomval);break;}case PROP_FRAMES_DISPLAYED:{g_value_set_int(value, qnxvideosink->frames_displayed);break;}case PROP_FRAME_TIME:{g_value_set_int(value, qnxvideosink->frame_time / 1000000);break;}
#endifdefault:{G_OBJECT_WARN_INVALID_PROPERTY_ID(object, prop_id, pspec);break;}}printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);
}static gboolean
gst_qnxvideo_sink_open(GstQnxVideoSink *qnxvideosink)
{printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);if (qnxvideosink->isOpened == FALSE){screen_create_context(&qnxvideosink->screen_ctx, SCREEN_APPLICATION_CONTEXT);screen_create_window(&qnxvideosink->screen_win, qnxvideosink->screen_ctx);int usage = GST_DISP_USAGE;screen_set_window_property_iv(qnxvideosink->screen_win, SCREEN_PROPERTY_USAGE, &usage);int format = SCREEN_FORMAT_NV12;screen_set_window_property_iv(qnxvideosink->screen_win, SCREEN_PROPERTY_FORMAT, &format);qnxvideosink->isOpened = TRUE;printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return TRUE;}printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return FALSE;
}static gboolean gst_qnxvideo_sink_close(GstQnxVideoSink *qnxvideosink)
{printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);if (qnxvideosink->isOpened == TRUE){if (qnxvideosink->screen_win){screen_destroy_window(qnxvideosink->screen_win);qnxvideosink->screen_win = NULL;}    if (qnxvideosink->screen_ctx){screen_destroy_context(qnxvideosink->screen_ctx);qnxvideosink->screen_ctx = NULL;    }printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return TRUE;}printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return FALSE;
}static GstStateChangeReturn
gst_qnxvideo_sink_change_state(GstElement *element, GstStateChange transition)
{printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);GstStateChangeReturn ret;switch (transition){case GST_STATE_CHANGE_NULL_TO_READY:break;case GST_STATE_CHANGE_READY_TO_PAUSED:if (!gst_qnxvideo_sink_open(GST_QNXVIDEOSINK(element)))goto open_failed;break;case GST_STATE_CHANGE_PAUSED_TO_PLAYING:break;default:break;}ret = GST_ELEMENT_CLASS(parent_class)->change_state(element, transition);switch (transition){case GST_STATE_CHANGE_PLAYING_TO_PAUSED:break;case GST_STATE_CHANGE_PAUSED_TO_READY:break;case GST_STATE_CHANGE_READY_TO_NULL:gst_qnxvideo_sink_close(GST_QNXVIDEOSINK(element));break;default:break;}printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return ret;open_failed:
{printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return GST_STATE_CHANGE_FAILURE;
}
}static gboolean plugin_init(GstPlugin *plugin)
{printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);if (!gst_element_register(plugin, "qnxvideosink", GST_RANK_SECONDARY, GST_TYPE_QNXVIDEOSINK)){printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return FALSE;}printf("[%s.%d]===>:\n", __FUNCTION__, __LINE__);return TRUE;
}GST_PLUGIN_DEFINE(GST_VERSION_MAJOR,GST_VERSION_MINOR,qnxvideo,"Qnx video sink",plugin_init, PLUGIN_VERSION, GST_LICENSE, GST_PACKAGE_NAME, GST_PACKAGE_ORIGIN);

注意， 输出的plugin动态库名称以 libpluginname.so 的形式， 而这个pluginname就是 编写插件时，定义插件的宏GST_PLUGIN_DEFINE 的参数中的name， 如果不匹配，就会出现插件无法是使用，被gstreamer将插件加入黑名单